Prevention of rust in pipe lines and tankers with acid-type wax oxidate



United States Patent Johan C. D. Onsterhout, Port Arthur, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware N0 Drawing. Application March 7, 1955 Serial No. 492,746

Claims. (Cl. 44-'70) This invention relates to preventing or retarding the rusting of metal bodies in contact with corrosive petroleum hydrocarbon liquids, such as gasoline, kerosene, diesel fuel and furnace oil. It is particularly concerned with preventing or retarding the rusting of iron pipe lines, and iron tanks as in tanker ships used to transport petroleum distillates of the above type. However, the principles may also be applied in other fields, as in protecting from corrosion heat exchangers carrying petroleum hydrocarbon.

Rusting frequently occurs in pipe lines and storage tanks when containing gasoline or other light distillates. This is in part believed due to moisture which is present in the pipe line or tank along with the distillate. Many chemical additives have been incorporated in light distillates to prevent or retard rusting. However, in the past it has not been possible to obtain completely satisfactory protection at a reasonably low cost.

Among the additives which have been suggested is oxidized microcrystalline Wax (petrolatum). While this material may give fair results in preventing rust, it has several undesirable drawbacks which are surmounted by the present invention. Among these drawbacks are.

(a) It has an excessively high viscosity, and thus is hard to dissolve and must be cut back with a great deal of solvent.

(b) It has a dark color which undesirably darkens gasoline and other light distillates.

(c) It increases gum values on gasoline undesirably.

(d) It imparts a cloudy appearance to gasoline.

(e) It emulsifies with water and may cause water in a pipe line or tanker to become dispersed in the gasoline or other light distillate.

I have discovered that improved corrosion inhibition at low cost is obtained without the drawbacks listed above, and with the additional advantage of corrosion inhibition in both the oil and water phases, by incorporating in a light petroleum distillate high acid content oxidized macrocrystalline wax having a neutralization number (Neut. No.) to saponification number (Sap. No.) ratio greater than 0.6. Advantageously, the oxidized wax should have a Neut. No. above 200 (desirably 200-300, with a target of about 230), a Sap. No. in the range 282-430, and an unsaponifiable content less than 40%.

The amount of the above acid type oxidized macrocrystalline wax included in the distillate may range from .5 to about 50 pounds (lbs.) per thousand barrels (M bbls.) of distillate. Typical concentrations that have been found highly useful in preventing rusting of iron surfaces are 3 to 6 lbs. of oxidate per M bbls. of light distillate passed through a pipe line; and about 12 to 18 lbs. of oxidate per M bbls. of light distillate in a tanker. The higher concentration is required in a tanker because the distillate is non-flowing, so that water tends to separate out and accumulate in the bottom of the tanks where it causes excessive corrosion. In a pipe line, on the other hand, water particles tend to remain suspended ice in the flowing distillate and cause less corrosion, thus requiring less oxidate.

For introducing the oxidate into a light distillate, it is advantageous to form first a concentrated additive solution of the oxidate in a solvent which is also soluble in the distillate to be inhibited. Such a solvent may be a light petroleum fraction such as benzene, toluene, kerosene or light diesel and gas oil fractions. A preferred solvent is an untreated kerosene distillate having a gravity of about 30 API, a flash point of about 160 F. (TCC), and an ASTM distillation 50% point of about 475 F. Proportions of about 1 part by weight of oxidate to 2 to 4 parts by weight of petroleum fraction are satisfactory, although other proportions may be used successfully. Solvent is advantageous because the oxidate is normally solid at room temperature and cannot be introduced directly in uniform proportions without cutting it back.

PREPARATION OF ACID-TYPE MACROCRYSTAL- LINE WAX OXIDATE High acid content macrocrystalline wax oxidates of low unsaponifiable content and excellent color characteristics are obtained by reacting a deoiled parafdn wax containing less than 5 percent oil with air in the presence of a catalyst at an air feed rate of about 10 to 50 cubic feet per pound of wax per hour, at a temperature between 230 and 290 F., and at a pressure of 30 to 300 pounds per square inch absolute. The wax oxidates obtained in a period of about 8 hours by use of the prescribed processing conditions are characterized by a Neut. No. above 200, and usually between 200 and 300; a Sap. No. above 282, and usually between 282 and 430; a Neut. No. to Sap. No. ratio greater than 0.6, usually 0.61 to 0.70; and an unsaponifiable content less than 40 percent.

The deoiled paraflin wax prescribed as a charge material is derived from lubricating oil distillates, is macrocrystalline in character, is predominantly aliphatic in nature, and contains between 20 and 33 carbon atoms per molecule. The preferred paraflin wax for use in this invention contains an average of 25 to 30 carbon atoms per molecule. Deoiled parafiin waxes meeting the specification of less than 5 percent oil are available as by-products of the manufacture of low pour lubricating oils. The deoiled wax is obtained from distillate lubricating oil fractions by solvent dewaxing or by pressing and sweating, and usually contains less than 3 percent oil. A preferred charge material for the process of the invention is obtained by solvent dewaxing a distillate oil which has been solvent refined With a solvent such as furfural, phenol, etc. A semi-refined wax of to 127 F. melting point obtained by solvent rewaxing a lube oil distillate is an example.

In general, the production of high acid content wax oxidates is effected in an aluminum-lined reactor in the presence of a catalyst. A particularly preferred catalyst is potassium permanganate which is charged to the reactor in 3 to 10 percent aqueous solution by weight together with deoiled parafiin wax, in amounts ranging from 0.01 to 1.0 percent of the total hydrocarbon charge by volume. Oil-soluble catalysts such as manganese stearate, zinc stearate, and manganese and zinc salts of previously oxidized wax fractions may also be employed in the process of this invention to produce the desired high acid type, oil-soluble macrocrystalline wax oxidates of .loW unsaponifiable content. A catalyst is advantageous because non-catalytic oxidation results in the production of ester-like oxidates.

During the oxidation, the temperature must be maintained within a fairly close range, namely, between 230 and 290 F. Advantageously, the reaction is eifected reaction is exothermic, means must be provided to contmuously remove the heat of reaction. Conventional means of indirect heat exchange are ordinarily employed to maintain the temperature within a F. range. An alternative means involves control of temperature by continuous introduction of water and removal of exothermic heat of reaction by evaporative cooling.

The use of the prescribed pressure range of 30 to 300 pounds per square inch is another important factor in producing a high acid content oxidate of the desired characteristics. The preferred pressure conditions are 50 to 200 pounds per square inch. The utilization of the specified pressure conditions not only results in the production of the desired type of oxidate, but also makes it possible to achieve the desired product in a commercially feasible period of time.

The final important factor in, the process of this invention is the rate at which air is passed through the oxidate. An air rate of 10 to 50 cubic feet of air per pound of parafiin per hour must be employed to obtain the desired product; air rates of 20 to 40 cubic feet per pound per hour comprise a preferred type of operation. Apparently air rates of the prescribed range result in the proper correlation of agitation and contact time to produce predominantly carboxyl groups at the prescribed temperature and pressure conditions. It should be noted that the amount of air passed through the reaction mixture is considerably in excess of that which actually enters into the reaction. It appears that the air rate has a two-fold efiect of defining the degree of agitation and prescribing the proper time of contact.

The process of the invention is illustrated in detail in the following examples wherein deoiled paraffins from various sources are subjected to air oxidation in accordance with the process of this invention. Particular attention is directed to the quality of the oxidate as illustrated by its Lovibond color, and the high acid content illustrated by the ratio of Neut. No. to Sap. No. of the product material.

Example I There was charged to an aluminum reactor provided with heat exchange surface 150 pounds of a wax obtained by solvent dewaxing paralfin-base distillate; the

There was also charged to the reactor an aqueous solution of potassium permanganate prepared by dissolving 0.6 pound of potassium permanganate in 10 pounds of water. Air blowing was initiated as soon as the total charge mixture was introduced into the reactor. The reaction mixture was rapidly heated to a temperature of about 340 F. by heat exchange in order to initiate the reaction. After initiation of the reaction was indicated by the evolution of heat, the reaction mass was rapidly cooled to an operating temperature of 270 F. During the induction period the pressure was adjusted to 80 p. s. i. a. and the air rate to 20 standard cubic feet of air per pound of wax per hour. The reaction was continued at the above mentioned conditions for a period of about 9 hours at which time the oxidate had reached a 263 Neut. No. There was obtained a yield of approximately 93 percent oxidate on the basis of hydrocarbon charged; the low molecular weight fractions which are entrained in the exit gases are not included in this yield. The product obtained was characterized by the following tests:

Neut. No 263 Sap. No 407 Unsap. matter, percent 9.7 Gravity, API 7.0 Flash, 0. Clev., F 300 Fire, Cleve, F 365 Visc., Say. Univ., at 210 F 84.3 Color, Lovi. /2" cell 60 Petrolatum melting point, "F 108.1 Ratio, Neut. No./Sap. No 0.65 Example II There was charged to an aluminum reactor provided with heat exchange surface 150 pounds of crude scale wax obtained by pressing and sweating a paraifin-base distillate. The charge wax had the following properties:

Gravity, API 43.4 Flash, 0. Cleve., F 420 Fire, Cleve., "F 480 Visc., Say. Univ., at 210 F 42.4 Color, Lovi., /2" cell 5 English melting point, F 128 Ash, percent 0.001 Sulfur, percent 0.02 Oil, percent ASTM 4.12

There was also charged to the reactor an aqueous solution of potassium permanganate prepared by dissolving 0.6 pound of potassium permanganate in 10 pounds of water. Air blowing was initiated as soon as the total charge mixture was introduced into the reactor. The reaction mixture was rapidly heated to a temperature of about 340 F. by heat exchange in order to initiate the reaction. After initiation of the reaction was indicated by heat evolution, the reaction mass was rapidly cooled to an operating temperature of 270 F. During both the induction period and reaction period pressure was maintained at p. s. i. a. and air rate was maintained at 20 standard cubic feet of air per pound of Wax per hour. The reaction'was continued at the above-mentioned conditions for a period of about 8 hours, at which time the oxidate had reached a Neut. No. of 264. There was obtained a yield of approximately 86 percent oxidate on the basis of hydrocarbon charged; the low molecular weight fractions removed from the reaction in the exit gases are not included in this yield. The product obtained was characterized by the following tests:

Neut. No 264 Sap. No 411 Unsap. matter, percent 9.3 Gravity, API 9.3 Flash, 0. Cleve, "F 280 Fire, Cleve., F -a 350 Visc., Say. Univ., at 210 F 80.6 Color, F. A. C 11A Petrolatum melting point "F 107 Ratio, Neut. No. to Sap. No 0.64

Although oxidate preparation has been illustrated with crude scale wax and a refined wax, it is applicable to other macrocrystalline waxes containing an oil content less than approximately 5 percent.

In preparing a concentrated acid type macrocrystalline wax oxidate solution in kerosene for addition to gasoline or the like, it is customary first to add about 1 part by volume of the oxidate as manufactured to about 2 parts of kerosene, agitate, and then allow to stand. Upon standing, two phases form, the supernatant top phase being a clear amber liquid which is drawn off and used as the corrosion inhibitor, while the bottom phase is a dark brown liquid which ordinarily is discarded. Both phases provide corrosion inhibition, but the bottom phase is less desirable because of its poorer solubility in gasoline, and its relatively dark color. The upper phase ordinarily contains 22-23% oxidate by volume, usually 22.5%.

Some solvents will dissolve the whole oxidate instead of causing phase separation. Among these are toluene and benzene.

Also, it should he noted that washing of the oxidate by agitation with hot water removes some of the materials which are least soluble in kerosene.

CORROSION INHIBITION The principles of the invention as applied to corrosion inhibition will be illustrated by the following specific examples which demonstrate the improved results obtained when inhibiting gasoline by incorporating therein high acid content oxidized macrocrystalline wax produced in accordance with the process described in detail above.

The tests employed to evaluate the inhibitors were as follows:

Rusting Test-1n this test a mixture of 300 ml. of gasoline with 30 ml. of distilled or synthetic sea water is shaken at a termperature of 80 F. for three hours with a cylindrical steel specimen completely immersed therein. Conditions otherwise are as described in ASTM test D-665-49T.

Quickie corrosion test.ln this test a polished steel strip is placed in a four ounce bottle containing 115 cc. of the test distillate at 90 F. The strip and distillate are then allowed to stand for 15 minutes. Next, 20 cc. of distillate are poured out and 20 cc. of distilled or synthetic sea water are added to the bottle, and the bottle is shaken for 15 seconds in a horizontal posi tion. The bottle is then turned to vertical position, given a short swirl to wash the water from the strip, and placed upright, Readings of the percentage of rust on the strip in the distillate phase are taken after three hours. Ordinarily considerable rust is expected on the portion of the strip in the water phase.

14 day cycling test.-This test procedure simulates tanker transportation service between a Texas refinery and an East Coast port when gasoline is hauled north and the return voyage is made under water ballast. The method consists of immersing for seven days in a tall 4 oz. bottle a weighed polished steel strip in contact with 5 cc. of synthetic sea Water and 110 cc. gaso line. The liquids are then removed and 115 cc. fresh salt water is added, after which there is an additional seven day storage period. The steel strip is then removed, cleaned and reweighed. The bottles are kept in an oven at 90 F. for the storage period.

Test Upper phase (A) Lowerl'ghase Appearance Amber Dark Brown. Spec. Grav., 60 I*./60 F 0.89 1.0771. Flas F 188 190. Vis., SUS 210 F 33 93. C01 5 (2" Lovib0nd) Brown.

Acetic acid extraction of the lower phase indicated the following compositions of the two phases:

Upper Lower Phase Phase Vol. Percent of Total 87.2 12. 8 Wt. Percent of TotaL- 85.0 15.0 Wt. Percent Oxidate 22-23 -100 Wt. Percent Kerosene 77-78 0-10 In corrosion tests the following results were obtained with the above materials, dosages being expressed in pounds of solution per thousand. barrels of distillate:

Example Illa ASTM RUSTING TEST Distilled Water Synthetic Sea Water Dosage, lbs./M bbls 0 5 0 15 Percent Rust On Bed Example I 14 DAY CYCLING TEST USING SYNTHETIC SEA WATER Dosage, Wt. Loss Percent Lbst/ After 14 Wt. Loss M Bbls. Days, Reduction mgs.

Upper Phase A 56 22. 5 60. 8 Lower Phase B 56 26.0 54. 7 Blank 0 57. 3

The following example illustrates results obtained with kerosene and toluene as solvents; and with washed and unwashed oxidates.

Example IV KEROSENE AND TOLUENE AS SOLVENTS Rusting tests with distilled water and gasoline were run on several different acid type macrocrystalline wax oxidates made from semi-refined wax and dissolved in kerosene and in toluene (about 1 part oxidate to 2 parts solvent by volume), with the following results:

Sample C D* E Oxidation Conditions- *Water-washed oxidate C.

EFFECT OB CONCENTRATION To show the effect of oxidate concentration on corrosion inhibition, quickie corrosion tests with distilled water were run with different dosages in gasoline of a naphtha-extracted and water-washed acid type wax oxidate made from 125-127 F. melting point semi-refined macrocrystalline wax by passing air therethrough at a temperature of 270 F., a pressure of 65 p. s. i. g., and a rate of 20 cu. ft./lb., using 0.4% KMnO catalyst.

The crude 230 Neut. No. acid type wax oxidate was mixed with an equal weight of water at 180 F. and mixed thoroughly. The water was drawn off after allowing adequate time for settling. This operation was repeated once.

The water-Washed oxidate was mixed with 2 parts by volume Stoddard Solvent at 150 F. Ample time was provided for settling and the insoluble portion was drawn E. The remaining soluble oxidate was stripped under vacuum.

The stripped oxidate, having a Neut. No. of 201 and a Sap. No. of 302, was blended with benzene to make the inhibitor concentrate. Dosages are based on the oxi- Example VI EFFECT OF NEUT. NO.

The effects of increasing Neut. No. were shown in quickie corrosion tests using a benzene solution of wax oxidate in gasoline and distilled water, as follows:

SAMPLE F G H Oxidation Conditions:

Time, Hrs 1% 8% 270 270 270 Visual Percent Rust On Iron Strips (Blank 50%) Dosage, lbs. oxidate/M bbls.:

1 Protected in both oil and water phases.

In the above examples gasoline was used as the test liquid because it is well known to be the most corrosive liquid transported in pipe lines and tankers. Obviously when gasoline is effectively inhibited by a selected oxidate, it can be expected that other less corrosive distillates will also be inhibited by the same oxidate.

Example VII Corrosion protection in the water phase is further shown by the following quickie corrosion test results with gasoline and distilled water:

Percent Source Stock Neut. Sap. Rust On Strip No. No.

Water Oil Phase Phase 200 208 349 0 0 Cryst. Wax 250 393 Example VIII EMULSIFICATION Equal portions of acid type petroleum and macrocrystalline wax oxidates were placed in water in glass containers and shaken vigorously. A completely stable emulsion was formed with the former, whereas with the latter some emulsification was obtained which separated in only a few minutes.

In color the acid type macrocrystalline wax oxidate is far lighter than acid type oxidates of petrolatum, which are reported as dark brown or black. On the Lovibond inch scale the color of a petrolatum oxidate has been reported as high as 6,000.

Additionally, the acid type macrocrystalline wax oxidat gives less trouble from gum formation in gasoline than does the petrolatum oxidate. In a standard ASTM gum test conducted in the laboratory, after 6 months of storage the gum from gasoline containing 15 pounds per thousand barrels of acid type petrolatum oxidate was 11 mgs./ cc., whereas acid type macrocrystalline wax oxidate under the same conditions gave only 4 mgs./ 100 From the foregoing laboratory test results it is apparent that the present invention provides an important improvement in preventing the corrosion of iron in the presence of petroleum distillates. The acid type macrocrystalline wax oxidate of this invention has also been used experimentally in sea-going tankers and in pipe lines. Visual observation has indicated that the predicted protection based on the laboratory tests has been realized, and rusting has been greatly reduced. In one pipeline transporting gasoline, test coupons indicate that essentially no corrosion has occurred during an experimental period of several months when using 3 pounds of oxidate per thousand barrels of gasoline. In an oil tanker rusting was greatly reduced when using experimentally 12 and 18 pounds of oxidate per thousand barrels respectively, during two periods of operation when cargoes included gasoline, kerosene, fuel oil, lubricating oil and diesel fuel.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A composition consisting essentially of a petroleum distillate having incorporated therein in a rust inhibiting amount, oxidized macrocrystalline paraflin wax having a Neut. No. between 200-300, a Sap. No. between 282- 430, a Neut. No. to Sap. No. ratio above 0.6, and an unsaponifiable content less than 40%.

2. A composition in accordance with claim 1 wherein said oxidized wax is present in an amount between about .5 and about 50 pounds per thousand barrels of distillate.

3. A composition in accordance with claim 1 wherein Said y talline wax contains 20 to 33 carbon atoms p m lecule.

4. A rust inhibitive additive for incorporation with a No. between 282430, a Neut. No. to Sap. No. ratio petroleum distillate for preventing rusting of iron pipe above 0.6, and an unsaponifiable content less than 40%.

lines, tanks, and the like containing said distillate, said additive consisting essentially of about 1 part by weight References Cited m the me of this patent of oxidized macrocrystalline paraffin wax having a Neut. 5 UNlTED STATES P T No. between 200-300, a Sap. No. between 282430, a

Neut. No. to Sap. No. ratio greater than 0.6 and an :33:1 ig g unsaponifiable content less than 40% dissolved in about 6 Zenner i 1949 2 to 4 parts by weight of a light petroleum solvent. 5 Zeuner 1949 5. A composition consisting essentially of a corrosive 10 Kleinhol'z 1954 petroleum hydrocarbonliquid having incorporated there- McKinley "i 1954 in in a rust inhibiting amount, oxidizing macrocrystalline 5 Kirk et a1 June 1954 parafiin wax having aNeut. No. between. 200-300, a Sap. 41 McKinley &';i""":"h 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,862,803 December 2, 1958 Johan 0 D. Oosterhout It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 53, for "rewaxing" read dewaxing column '7, line ll, in the table, third column thereof under the heading, "As

Oxidate", for the indistinct number read 92 Signed and sealed this 17th day of March 1959.

( A Attest:

KARL AXLINE ROBERT c. WATSON Attesting Officer Conmissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE F CORRECTION Patent No. 2,862,803 December 2, 1958 Johan C D. Oosterhout It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 53, for "rewancing read dewaxing column '7, line 11, in the table, third column thereof under the heading, "As

Oxidate", for the indistinct number read 92 Signed and sealed this 17th day of March 1959.

( A Attest:

KARL AXLINE ROBERT c. WATSON Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 2,862,803 December 2, 1958 Johan C D. Oosterhout It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below,

Column 2, line 53, for "rewaxing" read dewaxing column '7, line 11, in the table, third column thereof under the heading, "As Oxidate", for the indistinct number read 92 Signed and sealed this 17th day of March 1959.

(SEAL) Attest:

KARL AXLINE ROBERT c. WATSON Attesting Officer Commissioner of Patents 

1. A COMPOSITION CONSISTING ESSENTIALLY OF A PETROLEUM DISTILLATE HAVING INCORPORATED THEREIN IN A RUST INHIBITING AMOUNT, OXIDIZED MACROCRYSTALLINE PARAFFIN WAX HAVING A NEUT. NO. BETWEEN 200-300. A SAP. NO. BETWEEN 282430, A NEUT. NO. TO SAP. NO. RATIO ABOVE 0.6, AND AN UNSAPONIFIABLE CONTENT LESS THAN 40%. 